1. Operating Principles

Semiconductor laser diodes are based on the stimulated emission of photons resulting from the radiative recombination of electron-hole pairs within a forward-biased P-N junction. The choice of materials constituting the gain medium, as well as the engineering of their heterostructures, allows the emission wavelength to be precisely determined. When this amplifying medium is integrated into an optical resonant cavity, and provided that the optical gain compensates for all losses (absorption, scattering), coherent amplification of light via stimulated emission of radiation (Light Amplification by Stimulated Emission of Radiation, LASER) is achieved.

This first section presents the fundamental principles governing the operation of laser diodes. We will discuss the key design elements used to determine the device’s essential characteristics: emission wavelength, laser...